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Current definitions of tracheids and vessel elements are overly simple. These definitions are based on light microscope studies and have not incorporated information gained with scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Current definitions are based primarily on angiosperms, especially eudicots, and were devised before(More)
Xylem of the orchids studied provided unusually favorable material to demonstrate how conductive tissue evolves in monocotyledons. In the end walls of tracheary elements of many Orchidaceae, remnants of pit membranes were observed with scanning electron microscopy and minimally destructive methods. The full range from tracheids to vessel elements, featuring(More)
Ethylenediamine has been used as an agent for softening very hard woods prior to sectioning on a sliding microtome. The use of ethylenediamine is recommended for two additional uses: for preparing 1) soft woods in which wide, thin-walled tracheids or vessels tend to collapse during sliding microtome sectioning and 2) plant tissues with sclerenchyma mixed(More)
We have studied macerated xylem of ferns, supplemented by sections, by means of scanning electron microscopy (SEM) in a series of 20 papers, the results of which are summarized and interpreted here. Studies were based mostly on macerations, but also on some sections; these methods should be supplemented by other methods to confirm or modify the findings(More)
This species, which is quite similar in habit to A. nummularia Torr., is new to Texas. According to Woodson (in Ann. Mo. Bot. Gard. 41 : 94. 1954), this northcentral Mexican species was previously known to occur in the United States only in southern New Mexico. It is of interest to note that in addition to the Mexican states of Coahuila, San Luis Potosi and(More)